72 HISTORY OF PERSIA which he at length despatched to invade Persia was allowed to approach Rei without opposition, but there it was defeated by a smaller body under Tahir "the Ambi- dextrous/' who slew Amin's general, AH, with his left hand. This Tahir, a Persian by race, was the descendant of a slave who, upon securing his freedom, became a client of the Khuzai clan. He founded the Tahiri dynasty, which was to play a great part in Khorasan, and the present Amirs of Kain claim descent from him.1 After his victory Tahir assumed the offensive, and with the support of Harthama advanced on the capital by way of Ahwaz, defeating army after army on the way. Amin, distracted first by a rebellion in Syria and then by a conspiracy which was for a time successful, was in no position to withstand him. Receiving the allegiance of Arabia for his master, Tahir captured Wasit, and Baghdad alone remained loyal to the Caliph of the West, After a siege which lasted for a whole year the city was taken by storm. Amin, who had taken refuge in the citadel, then surrendered, and was put to death by the Khorasan soldiery. Rebellions in the Western Half of the Galiphat^ A.U. 198..... 201 (813-816),—But the struggle between the Persian and the Arabian halves of the Caliphate was not ended by the death of Amin. By an act of folly Tahir after his victories was removed from the supreme command in favour of Hasan, brother of Fazl, the Persian Vizier, and although he was appointed Governor of Syria and Mesopotamia instead, he was naturally disinclined to take active steps, and remained at Ricca a passive spectator of events. Mamun apparently determined to make Mervs his capital and did not appear at Baghdad* In consequence, a rising was fomented at Kufa in favour of the House of Ali, and other rebellions broke out in Asia Minor and Arabia. Harthama, faithful to Mamun, travelled to 1 Ten Thousand Miks^ etc., p. 399. 2 According to Yakut, the following «ying is attributed to Mimwn; "There ire three thing* at Mcrv which the poor enjoy as well a* the rich, to wit, it» deliciou* melons, its water, which ia always fresh owing; to the abundance of the »now*> and iu downy cotton."